1. Field of the Invention
The present invention relates to an ultrasonic probe and an ultrasonic diagnosis apparatus having a two-dimensional array structure, and an ultrasonic probe manufacturing method.
2. Description of the Related Art
An ultrasonic probe having a one-dimensional array structure is available. A transducer unit included in this one-dimensional array ultrasonic probe has a plurality of transducers arrayed in a line. In general, electrodes on the upper and lower surfaces of the transducer unit are extracted from an end of the transducer unit. Various contrivances have been made to extract upper surface electrodes. For example, there is available a technique of electrically extracting upper surface electrodes from the lower surface of a transducer unit via an FPC (Flexible Printed Circuit board) by plating a side surface of the transducer unit to render the upper and lower surfaces conductive. The signals extracted by the FPC are transmitted to a transmission/reception circuit via a probe cable.
In general, the acoustic impedance of polyimide used as a base material for an FPC is about 3 MRayl. The acoustic impedance of a transducer unit is equal to or more than 30 MRayl. For this reason, when the FPC is directly joined to the transducer unit, an acoustic mismatch occurs. In order to reduce this acoustic mismatch, an acoustic matching layer having an acoustic impedance between 3 MRayl and 30 MRayl is used. This acoustic matching layer is placed on the upper surface of the transducer unit, and the FPC is placed on the upper surface of the placed acoustic matching layer. Upper surface electrodes are electrically extracted via this FPC.
In the case of specifications with three acoustic matching layers added to a transducer unit, the first acoustic matching layer has the best acoustic impedance of about 9 to 15 MRayl. A material having such an acoustic impedance is a ceramic material containing mica as a main component. This ceramic material is known as a machinable ceramic material. This material has non-conductivity. There is a technique uses a method of plating all the surfaces of the first acoustic matching layer using this non-conductive material and electrically extracting upper surface electrodes formed out of a piezoelectric element to the upper surface of the acoustic matching layer.
In a three-layer specification two-dimensional array ultrasonic probe, a multilayer structure comprising a plate-like piezoelectric member, a first acoustic matching layer member, and a second acoustic matching layer member is cut in a lattice form. With this cutting, each acoustic matching layer is divided into a plurality of acoustic matching elements arrayed two-dimensionally. In the above method of extracting upper surface electrodes by plating the surrounding portion, the upper and lower surfaces of acoustic matching elements other than those located outside the first acoustic matching layer are not rendered conductive.
As another method of electrically extracting upper surface electrodes to the upper surface of an acoustic matching layer, a method of attaching a conductive pattern to a side surface of an acoustic matching layer has been proposed. In this method, however, pattern attachment processing needs to be performed for each column. This increases the number of steps, resulting in an increase in cost.